Electric discharge tube circuits



Dec. 18, 1956 F. H. BRAY EI'AL ELECTRIC DISCHARGE TUBE CIRCUITS Fi'led Jan. 30,' 1953 2 Sheets-Sheet 2 m||| 2 3 p I 2 u flun my 32 G M! G H V V 2 I i I I I Ill-x e. HARTLEY B) ATTORNEY ELECTRIC DISCHARGE TUBE CIRCUITS Frederick Harry Bray, Ronald George Knight, and George Clitiord Hartley, London, England, assignors to International Standard Electric Corporation, New York,

Application January 30, 1953, Serial No. 334,192

Claims priority, application Great Britain February 13, 1952 6 Claims. (Cl. 179--18) This invention relates to electric circuit switching by means of cold cathode gas discharge tubes.

The object of the invention is the establishment of a connection or' connections out of a number of possible connections through one or more anode-cathode gapsof cold cathode gas discharge tubes. 7

One aspect of the invention comprises an electric switch comprising a first circuit, and a numberof additional circuits, and switching means intermediate said first circuit and said additional circuits, such that operation of said switching means in response to conditions of availability of said first circuit and one of said additionalcircuits automatically connects together said pair of circuits to the exclusion of any other additional circuit and causes a change in the electrical conditions of said interconnected circuits to busy said circuits against other connections.

The invention willbe particularly described withrespect to the accompanying drawings in which:

Figs. 1 and 2 show known circuits for firing gas discharge tubes',

Figs. 3 and4 show novel circuits in accordance with the invention for firing gasdischarge tubes,

Fig. 5 shows the application of the circuit of Fig. 3' to a multi-gap gas discharge tube,-

Fig. 6 shows the interrelation of electric pulse cycles used in the operation of the circuit of Fig. 5,

Fig. 7 shows a switching circuit for connecting any one of a first group of lines to any one of a second group of lines, broadly similar in function to the conventional line switch group of an automatic telecommunication exchange, while Fig. 8 shows the interrelation of electric pulse cycles usedin the operation ofthe circuit of Fig; 7.

Considering first a simple gasdischarge gap having an anode and a cathode, ionisation of the gas occurs when avoltage, in. excess of what is. commonly called the breakdown or firing voltage of the gap, is applied between the anode and the cathode. Having broken down, the gap will continue to pass current or discharge until the nited States Patent 0 a voltage between the anode and the cathode is reduced 1 below what is commonly called the maintaining voltage of the gap.

Figs. 1 and-2 show known circuit arrangements whereby a single gap in a gas discharge tube G having an anode A and a cathode C and a-ga-p therebetween may be connected across a source of potential and caused to break down and pass current by the application of one or more poten-- tials at different points-in the circuit.

Referring first to Fig. 1, the tube- G is connected between a potential +V and earth through an anode resist-- ance R1 and a cathode rectifier W1 arranged in conduct ing direction. The potential |V is insuificient to-fire the tube G but sutficient to maintain it in conducting condi tion when fired.

Application to the cathode C of a potential P through a high resistance R3 causes the tube G to fire,

2,774,820 Patented Dec. 18, 1956 the total potential +VP being suflicient to break down the gap. Current flows, the rectifier W1 conducts and becomes low or negligible in resistance compared to R3 and the potential 'P which caused the breakdown becomes inefiecti-ve due to voltage drop across the high resistance R3. Referring now to Fig. 2 the tube G is connected between a potential +V and earth as before but with rectifier W2 in the anode circuit and resistance R2 in the cathode circuit. Application to the anode of a potential +Q through high resistance R4 and greater than. potential {-V causes tube G to fire, the potential +Q to earth being sufiicient to break down the gap. Current flows, the rectifier W2 conducts and becomes of low resistance compared to R4 and the potential +Q becomes ineifective through the high resistance R4.

Turning now to Fig. 3, which shows an embodiment of the invention, firing of the tube is caused to occur by the coincident application of two potentials to the circuit, one on the anode side of the tube and one on the cathode side. Tube G is connected between potential +V and earth through anode rectifier W2 and resistance R1, and cathode resistance R2 and rectifier W1, and the potentials on the anode and cathode respectively will be referred to hereinafter as non-available potentials. A potential +Q is applied to the anode A through high resistance R4 and resistance R1, and a potential -P' is applied to the cathode C through high resistance R3 and resistance R2. The values of +Q and P', which will hereinafter be referred to as available potentials, are such that the tube may be subjected to four different potentials, only one of which is efiective to fire the gap. These four potentials are:

(a) +V to earth which may be regarded as the normal circuit condition with the tube unfired.

(b) +Q to earth when only +Q' is applied and not -P'. This potential is insuihcient either to fire the tube or to maintain it through high resistance R4, if it has become fired in some other manner.

(0) +V to P. This potential is also insuificient either to fire the tube or to maintain it through high resistance R3.

(d) +Q to -P. In this condition, that is to say, with the coincident application of both potentials +Q' and -P to the circuit, sufiicient potential is produced across the tube to fire the gap but not to maintain it through either of high resistances R3 or R4.

As in Figs. 1 and 2, current flows, and the rectifier W1, W2,-.cond uct and the potentials +Q and P become inefiective through high resistances R4 and R3; in other words busy potential is applied toeach electrode.

One example of reduction to practice of the circuit of Fig. 3 is shown in Fig. 4 in which the potentials used are indicated. The break-down voltage of the tube is 400 v. and the minimummaintaining voltage is 180 v., while the forward resistance of the rectifiers is in the neighbourhood of 1000 ohms and their reverse resistances 10 megohms. For convenience the centre point of the battery was earthed instead of the negative pole. The anode and" cathode series resistances whose function is to safeguard the tube against overloading, caneach be varied between zero and 60,000 ohms. However, values of 15,000 ohms are normally used.

Fig. 5 shows a circuit arrangement in which a multigap gas discharge tube is employed, such as a multi cathode single-anode tube. Such tubes are known in which the firing of one gap does not prime or apprecia manner similar to that explained in connection with Fig. 3. That is to say, the potential l-V is sufliclent to maintain but not fire any one of the gaps and only the application of a potential +Q to the anode through a high resistance R4 and resistance R1, together with the application of a potential P' to one of the cathodes through a high resistance R3 and resistance R2 will apply available potentials to both electrodes and cause breakdown of the appropriate gap. Since, as already explained, the potentials +Q and P' are inelfective after the gap is struck, either or both may be of any momentary application provided they are coincident.

Consider in a supply of P' pulses, Pl, P'Z Pn occurring in a time interval T, throughout which interval a pulse +Q' also occurs. Such an arrangement is shown graphically in Fig. 6. Consider also an arrangement whereby each of the train of P' pulses is distributed, in well known manner, to a different one of the cathodes, as indicated in Fig. 5. At the beginning of time interval T, +Q will be present on the anode A and P', will be present on the first cathode and the first gap will fire and maintain from l-V.

As already stated, the construction of the tube is such that ionisation does not spread to any other gap nor is the break-down voltage of any other gap appreciably reduced.

When the next pulse P2 arrives, it will be ineffective to fire the second gap, because the potential +Q, although still being applied through R4, is ineffective through high resistance R4 to raise the potential of the anode A as already described; in other words, there is busy potential on the anode.

In like manner subsequent pulses will also be ineffective. In the event, for some reason, the pulse P']. is suppressed so that the first gap does not fire, then pulse PZ will be effective to fire the second gap and the remaining pulses will be ineffective. In a similar manner any desired one of the gaps can be fired.

It will now be explained how such an arrangement may be employed for interconnecting one of a group of circuits with one of another group of circuits.

Assume that a circuit of a group X comprising x circuits is to be connected to a circuit of a group Y comprising y circuits. Referring to Fig. 7, there are provided a number of multi-cathode tubes G1 Gx, of the kind described, equal to the number of circuits x in group X, each tube having a number of cathodes equal to the number of circuits y in group Y. In the event the tubes contain less than y cathodes, two or more tubes may have their anodes connected together and be regarded as one tube. Each of the circuits in group X is connected to the anode of a different tube through an individual limiting resistance R1 and also provides, through individual rectifiers W2, a potential +V. Each of the circuits of group Y is connected through an individual limiting resistance R2 to a different cathode of the first tube G1 and is multiplied through individual resistances R2 to corresponding cathodes in each of the other tubes G2-Gx, so that no cathode of any tube has more than one circuit connected to it. The individual resistances R2 may be replaced by common resistances, immediately to the right of the multiple points. The circuits Y may if desired, be connected in different orders to the cathodes of the different tubes. Each of the circuits of group Y also provides earth through an individual rectifier W1. The direction of connection of the rectifiers W1 and W2 is such that current can flow from +V, through an appropriately ionised gap in a tube, to earth.

A series of positive pulses +Q1 +Qx is allotted, one each, to the 1 x circuits of group X and a series of negative pulses Pl P'y is allotted, one each, to the 1 y circuits of group Y, making the X and Y circuits individually available in turn.

The negative pulses P'l -Py are applied p91)- 4 tinuously to the 1 circuits of group Y, each through a high resistance R3. The positive pulses +Q'1 +Q'x, each through a high resistance R4,

are not normally applied to the 1 x circuits but the appropriate pulse is applied by a circuit of the X group which requires a connection to a circuit of the Y group. The time pulse relationship of these two series of pulses is shown graphically in Fig. 8, from which it will be seen that each of the positive pulses occurs one after the other in a cycle time T and each of the negative pulses occurs one after the other within the individual time of a single one of the positive pulses. Thus during time T each positive pulse occurs once in conjunction with each negative pulse.

Returning to Fig. 7, it is assumed that circuit No. 2 of group X is to be connected to a free circuit in group Y and that circuits Nos. 1, 2, 7, in group Y are busy in some manner, for instance through other tubes not shown, such that their pulses P'l, P2 and P'7 are ineffective through their respective high resistances R3 in a manner already described.

Circuit No. 2 of group X applies pulse +Q'2 to the anode of tube G2. Pulses Pl P'y are, as already stated, being continuously applied in turn, but pulses P'1, P'2 and P'7 are ineffective through their high resistances R3 due to circuits Nos. 1, 2 and 7 of group Y being busy as already described. When one of the other negative pulses coincides with +Q'2, the appropriate gap in tube G2 will fire, due to there being available potentials on both electrodes. For instance, if the +Q2 pulse supply of No. 2 circuit of group X is connected during an interval between the appearances of pulse +Q2, the first negative pulse which will coincide with it when it does appear will be -P'3, and gap No. 3 of tube G2 will fire and circuit No. 2 of group X will be connected through the gap to circuit No. 3 of group Y. If, on the other hand, the pulse circuit of No. 2 circuit of group X is closed during the appearance of pulse +Q'2, the connection will depend upon which negative pulse is appearing at the time. For instance, if P'7 is appearing it will be ineffective, as already explained, and P8 will cause firing of gap 8 in tube G2. If, on the other hand, Py is appearing, gap y will fire and circuit No. 2 of group X will be connected through gap y to circuit y of group Y.

The firing of a gap busies the circuits connected to both electrodes.

In order to release two circuits thus connected together, removal of +V by the X circuit in any suitable manner, as by relay contacts, or of earth by the Y circuit, will extinguish the fired gap through which they were connected.

It will be appreciated that two or more circuits in group X may simultaneously require connection to a circuit in group Y and that such simultaneous requirements will be met without mutual interference in one cycle time T by coincidence of the appropriate pairs of and pulses. Thus during a busy period any or all of the X group circuits may simultaneously or at irregular intervals be connected to Y group circuits in random order of arrangement, and without mutual interference either during connecting up or while connected up or during release.

While the invention, as shown in Figs. 5 and 7, has been described in connection with multi-cathode tubes, it will be understood that multi-alnode tubes may be used with appropriate modifications to the circuits or a plurality of single gap tubes may be used, their anodes or cathodes being connected together, as already described. Moreover, the limiting resistances R1 and R2 may be varied or eliminated without departing from the substance of the invention.

Other modifications may be made. For instance, the positive potentials in connection with Figs. 7 and 8 may be of short duration and the negative potentials of long duration, such that each positive potential appears once during each appearance of each negative potential. If it is desired to switch more than one lead simultaneously, a plurality of sets of equipment identical with those shown in Figs. 5 and 7 can be provided, each corresponding plurality of pulse leads being connected to the same pulse source. In this way, application of a +Q pulse will cause a plurality of gaps to fire, one in each set of equipment, and a two-, three-, or more, wire connection could be set up.

It is of course possible that one or more of the P1 circuits would not be connected to the respective cathode in every one of the tubes G1, GZ-Gx, since some form of grading of these circuits might be desired, but it is to be understood that any such variation of the complete switching arrangement is within the scope of the invention.

While the principles of the invention have been described above in connection with specific embodiments and particular modifications thereof, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention.

What we claim is:

l. A static electrical switch comprising a plurality of groups of cold cathode gas discharge gaps having anode and cathode electrodes, an equal plurality of circuits constituting a first group each circuit multipled to one electrode of a respective group of gaps, a number of cincuits constituting a second group each circuit multipled to the other electrode in each of said groups of gaps, the circuits of both said first and second groups of circuits being individually adapted to assume any one of three difierent electrical conditions in respect of said gaps: the

first condition representing non-availability, a second condition representing availability, and a third condition representing that the line is busy, means for biasing said anode and cathode electrodes of said gaps so that no gap will fire unless the connected circuits are simultaneously in the electrical condition representing availability, means for changing the electrical conditions of said first group of circuits from a condition representing nonavailability to one representing availability in turn in a first cycle of time positions, means for changing the electrical conditions of said second group of circuits from a condition representing non-availability to one representing availability in turn in a second cycle of time position, said first and second cycle of time positions being such that pairs of circuits each consisting of a circuit of the first group and a circuit of the second group can be ofiered to one another in a condition representing availability in time positions individual to each pair, whereby a circuit of the first group can be connected to a circuit of the second group to the exclusion of all other circuits by firing of the gap individual to said pair of circuits in the time position individual thereto, and means for automatically changing the electrical condition of a pair of :circuits to one representing that the circuits are busy when the respective gap is fired.

2. A static electrical switch, as claimed in claim 1, and in which each individual circuit comprises a potential lead including a rectifier, and a pulse lead including a high resistance connected in parallel via a resistance to the respective gap electrode.

3. An automatic telecommunication exchange switch of the static electrical type comprising a set of cold cathode gas discharge transmission paths for interconnecting a first telecommunication transmission circuit and any one of a group of other telecommunication transmission circuits, said paths comprising anode and cathode electrodes and means for establishing the corresponding gas discharge path at a time position in an unvariable sequence of time positions in which each time position is individual to one of said other circuits, said means comprising means for applying a potential to the electrode of said path which is connected to said other circuit during said respective time position, said potential being sufficient to establish the discharge path.

4. An automatic telecommunication exchange switch of the static electrical type comprising two sets of gas discharge transmission paths for interconnecting a first two-wire telecommunication transmission circuit and any one of a group of other two-wire telecommunication transmission cincuits, said paths comprising anode and cathode electrodes, and means for simultaneously establishing the corresponding pair of gas discharge transmission paths at a time position in an unvariable sequence of time positions in which each position is individual to one of said other two-wire circuits, said means comprising means for applying a potential to the electrodes of said paths which are connected to said other two-wire circuits during said respective time positions, said potential being sufficient to establish the discharge paths.

5. An automatic telecommunication exchange switch of the static electrical type comprising three or more sets of gas discharge transmission paths for interconnecting a first three or more wire telecommunication transmission cincuit and any one of a group of other three or more wire telecommunication transmission circuits, said paths comprising anode and cathode electrodes, and means for simultaneously establishing the corresponding three or more gas discharge transmission paths at a time position in an unvariable sequence of time positions in which each position is individual to one of said other three or more wire circuits, said switch means comprising means for applying a potential to the electrodes of said paths which are connected to said other three or more wire circuits during said respective time position, such potential being sufficient to establish the discharge paths.

6. An automatic telecommunication exchange switch of the static electrical type comprising a set of cold cathode gas discharge transmission paths for interconnecting a first telecommunication transmission circuit and any one of a group of other telecommunication circuits, said paths comprising anode and cathode electrodes, said first circuit being connected to all the corresponding electrodes of said set and said other circuits being connected respectively to said other corresponding electrodes, each said other circuit comprising a coincidence gate having two inputs and means for applying a potential on the electrode connected to said circuit sutficient to cause a discharge when predetermined potentials are simultaneously applied to said inputs, means for applying said predetermined potential to a corresponding one of said inputs of each of said coincidence gates at a time position in an unvariable sequence of time positions, whereby each of said other circuits is offered for connection to said first circuit during a different time position.

References Cited in the file of this patent UNITED STATES PATENTS 1,677,414 Stehlik July 17, 1928 2,299,229 Hall Oct. 20, 1942 2,549,064 Depp Ap 17. 2,553,263 Loughren May 15, 1951 2,560,691 Hagen July 17, 1951 2,562,100 Holden July 24, 1951 2,607,891 Townsend Aug. 19, 1952 2,648,831 Vroom Aug. 11, 1953 2,722,567 Davison et a1. Nov. 1,1955 

